Our long-term goal is to elucidate one of the fundamental aspects of cholesterol metabolism: delivery of the hydrophobic cholesterol molecule through the hydrophilic cellular matrix and the physiological importance of this process. The inability to synthesize cholesterol makes insects highly dependent on the efficient transport mechanisms involved in cellular sterol translocation. We have been investigating the role of a mosquito sterol carrier protein-2 (AeSCP-2) in intracellular cholesterol transfer. The specific hypothesis is that AeSCP-2 is a vital link in the process. This hypothesis is based on the observations that silencing AeSCP-2 expression in Aedes aegypti larvae results in decreased incorporation of cholesterol in vivo and a high mortality rate in mosquitoes. We have identified several AeSCP-2 inhibitors (SCPIs) via high throughput screening of a small chemical library. Inhibition of AeSCP-2 function using the newly discovered inhibitors suppresses cholesterol uptake in vivo and results in a high mortality rate in mosquito larvae. SCPIs are effective larvicides in Aedes aegypti, Anopheles gambiae and Culex pipiens, indicating that a sterol carrier protein-2 has functional similarity in different mosquito species. Specific aim 1: Determine the mechanism of AeSCP-2 mediated intracellular cholesterol in a cell culture model system. We will correlate the presence and the function of wild-type and mutated AeSCP-2 to cholesterol uptake and cholesterol redistribution within the cultured cells. Specific aim 2: Examine the roles of AeSCP-2 in coordinating the absorption of sterols and cholesterol using newly discovered inhibitors and RNA interference (RNAi) in a mosquito organism model system. Specific aim 3: Determine the transcriptional regulation of the AeSCP-2 gene. Expression of the AeSCP-2 gene is correlated with physiological processes in which the demand for cholesterol absorption and redistribution is high. Important transcription factors that coordinate physiological events in cholesterol metabolism will be identified through the study of the AeSCP-2 gene. Results from this study will yield insightful information involving the function of sterol carrier protein-2 and will shed light on the regulation of the gene. The results will also validate the potential of targeting cholesterol metabolism for the development of new strategies to control mosquito populations.